Abstract: Exhaust gas recirculation (EGR) is an effective strategy to control NOx emissions from diesel engines. In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NO. Car manufacturers are having to make adaptations to the designs of their vehicles to meet the stringent limits. I've seen a lot of cars which came in our car shop with EGR faults, the check engine fault. Most modern cars utilise an electronically controlled EGR which is controlled by the vehicle's engine control module (ECM). The Exhaust Gas Recirculation or EGR system is one of several vehicle emission control systems.